For mellow lighting I started using candle lamps, which I may post photos of later. But I found they don't provide very good light for reading or small work.
I thought of trying LED lights, but found most of the solutions available either expensive or not small enough to suit me. Then one day walking through Home Despot I walked by my solution: LED headlamps. I already had a headlamp for night hiking and working outside after dark, but until I saw ungodly cheap headlamps I didn't consider hacking them up for the van.
I bought some of the cheap headlamps, cut off the straps, and applied velcro to the forehead pad. For mounting brackets I took small scrap pieces of aluminum (the mounting brackets from VW horns) and applied the other half of the velcro to them. I then picked existing screws in places I wanted light and attached the brackets. I have one bracket on each side of the stock 12v light, two on the bottom side of the top bunk, one on a screw that holds the roof vent on, and one in the closet. When not in use I store the lamps in the silverware drawer.
For an additional lighting option, I use a headlamp we have for the bicycle clamped to the poptop bar. It can be left in place when the top is lowered.
I use rechargeable batteries and have a solar charger, so the solution is reasonably green. So far I'm really happy with the setup, I can easily vary the amount of light in the van and if I ever want to turn it back to stock look it'll take five minutes and a screw driver.
x-posted in a slightly different from to eor